Chicago police Superintendent Eddie Johnson was awake and alert and already checking his email a day after undergoing a kidney transplant, his surgeons said Thursday.

The city's top cop will remained hospitalized at Rush University Medical Center for several more days as he recovers, though his son Daniel Johnson, 25, who donated the kidney, was expected to be released Thursday.

"The superintendent looks really good. He's awake. He's sitting up. He's probably by now sitting in a chair," one of his surgeons, Dr. Edward Hollinger, told reporters at Rush during a Thursday news conference.

Through Hollinger, Johnson expressed to the public "how grateful he is for the well-wishes that he's gotten and he's really felt the outpouring of good wishes."

Doctors "expect a full recovery" for Johnson, who will be on leave for at least six weeks, according to Rush transplant nephrologist, Vasil Peev. Over time, his mobility will improve — he will be able to sit at a desk and walk without limitation by next week — but he won't be able to exercise or lift heavy objects for several months.

But before Johnson is cleared to go home this weekend, his doctors say they will be keeping a watchful eye for any signs of rejection of his new kidney, or infection, which doctors said was rare.

There were already signs that Johnson was eager to get back to work. "I heard that he was (checking) emails already last night, so he's back in business," said Dr. Martin Heitl, Rush's division chief of transplant surgery.

Johnson's absence will have "no operational impact" on his department as his first deputy superintendent, Kevin Navarro, is acting on his behalf, a spokesman said.

Johnson's doctors say he will not have to undergo a strict diet now that he has a working kidney, though patients waiting for transplants, or undergoing dialysis must follow a stricter dietary regimen, Peev said.

The doctors and officials with Gift of Hope, a not-for-profit organ procurement organization, said they hoped Johnson's ordeal will move others to become organ donors and make a dent in the thousands of patients waiting for organ donations.

Johnson, who turned 57 in July, was his son's age when he was diagnosed with glomerulonephritis, an acute inflammation of the kidney. Johnson found out about the disease during a doctor's visit as part of his application process to become a Chicago police officer. At the time of his diagnosis, doctors thought his kidneys would last only four or five years.